In order to investigate the dependence of radiobiological effects on energy distribution in cells, the latter are irradiated with molecular ions. When striking matter, these ions dissociate and pairs or triplets of particles traverse the cells with mean separations that can be varied. In addition, the effects of equal numbers of randomly incident particles can be determined. The results support the theory of dual radiation action and provide numerical parameters for its application. The cells irradiated are Chinese hamster cells in tissue culture and the effects assessed are reproductive cell death and chromosome aberrations.